RUBUS STRIGOSUS. 95 



RUBUS STRIGOSUS. 



General relations. — The raspberry is especially well fitted to serve as 

 a standard plant for competition studies, owing to its abundant nectar and 

 pollen, the duration of the flowering period, and its exceptional attractiveness 

 for the honey-bee. While it is employed as the standard plant for the 

 majority of the following experiments, certain reciprocal comparisons were 

 made in which it was the bouquet. The various species with which it 

 competed practically all possess open flowers, but exhibit a wide range in 

 the size and color of the latter and the amount of nectar and pollen, as well 

 as in the degree of relationship. With respect to the latter, Rubus deliciosus 

 represents a related species, Rosa a related and Opulaster a more distant 

 genus of the same family, while Geranium, Cleome, and Frasera are succes- 

 sively more remote, exemplifying a progressive decrease in the number of 

 stamens and pistils, as well as striking differences in the nectaries. Mer- 

 tensia and Pentstemon afford more pronounced differences, though these are 

 still within the range of effective competition. The order of treatment in 

 the following pages is essentially that of degree of relationship, though the 

 effect of size, color, and amount of nectar or pollen often obscures the signi- 

 ficance of this. 



RUBUS STRIGOSUS AND RUBUS DELICIOSUS. 



Comparison. — The flowers of the raspberry are small and inconspicuous 

 and more or less hidden by the leaves, so that they are hardly noticeable, 

 while those of the salmonberry are large and showy and stand out clearly 

 from the leaves on most of the branches. The flowers of both are white, 

 but the corolla of Rubus strigosus is masked to a large degree by the green 

 sepals. The flowers of the latter are often more numerous in an equal 

 area, but they are so scattered as to be quite ineffective. Pollen is naturally 

 abundant in both species, but there is approximately eight times as much 

 in R. deliciosus. The petals of the latter are expanded at right angles to 

 the pedicel, leaving the stamens much exposed, while in R. strigosus the 

 petals are more or less erect and the pollen consequently less accessible. 

 The nectar of R. deliciosus is formed at the base of the stamens and appears 

 as minute drops in a circle; it is produced in the same place in R. strigosus, 

 but much more abundantly, sometimes accumulating to an appreciable 

 depth in the stamen-tube (plate 3). 



Experiments. — Of the five studies made with these two species, Rubus 

 strigosus was employed as the standard plant in the first three, and R. 

 deliciosus in the last two. Two observers recorded the visitors in each 

 case, and the numbers consequently are not only exact, but they are also 

 maximum. In all cases where two figures are separated by a colon, the 

 first indicates the number of insects and the second the number of visits 

 made by them. 



The differences arising out of the time-factor are revealed by the totals, 

 the number of visitors being nearly twice as great in the first experiment. 

 During the third period, Rubus deliciosus received several times as many 

 visitors, due in part to the presence of the two species of flies. All told, 

 Apis furnished 171 visitors to the raspberry in contrast to 5 for the salmon- 



